pcs has a control option for the 6l80/90 transmission now in a stand alone. The swappable bell housing cars make it an ideal choice, a custom cast bell housing could be made, a machined flex plate but I'm not sure about the converter sizes available.

I also considered using a gm ecm with a jumper harness to pull out sensor data it would require to emulate a running engine. Would require the 58 tooth reluctor with a pickup. It would require research on the other sensor data compatibility as to what could be used from the N54. Worst case additional sensors could be used perhaps. IMO, the power capabilities of a 6l90 along with its shift chatacteristics and torque converter stall change availability would bring this platform to a completely new level!